A plethora of prior art devices exist for portable collapsible child's play-pens. A few of such devices are described and illustrated in the following patents, namely U.S. Pat. Nos. 3,699,594, 4,819,285, 4,044,411, 4,692,953, 5,197,154, 3,722,009, 4,811,437, 4,097,942, 5,228,154, 5,243,718 and 5,279,006, as well as the applicant's co-pending U.S. application Ser. No. 08/384,887 filed Feb. 3, 1995.
As may be seen from the above patents, a number of these devices make use of foldable half members, which when the walls of the play-pen are collapsed onto the half-members, and they are then folded together, may be used as a portable carrying case for the play-pen.
Some of these, specifically for example U.S. Pat. No. 3,699,594, teach an ingenious design, having foldable end members 18 and 19, and side frame members 24, 25 and 26, 27, which may be folded onto end members 18, 19, and the end members may then be collapsed onto half-shells 1 and 2. It has not been immediately apparent, however, how to improve the design of U.S. Pat. No. 3,699,594 to eliminate metal or wood structural elements in the side walls which retain and support the side walls to thereby eliminate the weight problem such members cause, yet still maintain a sturdy, lightweight, and most importantly an easily collapsible and portable structure.
A number of attempts at using lightweight fabric as wall material to thereby reduce the weight of the play-pen have been put forward, such as U.S. Pat. No. 4,044,411, 4,692,953, and 4,819,285. The first two of these patents also incorporate a zipper. While these patents are ingenious in their manner of collapse and folding, they generally have other drawbacks unique to that particular design, which reduces the practicality or usefulness of the design. For example, U.S. Pat. No. 4,819,285, which incorporates a flexible fabric netting for the side walls, and also hinges 134, 132 proximate the mid-section of bottom rail tubes 130, 135 and 128, 133 respectively, necessarily requires top rail tubes 124 and 126 which are secured by snap fittings 210 to bottom rail tubes 128, 130, 133 and 135 (see FIGS. 1, 2, and 4). These necessary additional top rail tubes 124, 128 add further weight, reducing the portability of the crib.
Likewise, U.S. Pat. No. 4,692,943 teaches a portable collapsible crib which includes a rigid first top rail tube 28 and a rigid second top rail tube 30, each separately hinged at midpoint 29 and 31 respectively by a first hinge 32 and second hinge 34 (see FIG. 4 and Col. 3, line 40-45). Notably, however, to set up the crib, the design requires that the entire crib must be lifted so as to be able to pivot legs 48 and 50, and then legs 52 and 54, so as to place them under the base of the unit 88 to thereby suspend the crib from the newly erected legs. This requires considerable dexterity and some strength to simultaneously lift the crib and at the same time position the feet under the lifted crib.
In the same manner, U.S. Pat. No. 4,044,411 possesses drawbacks, in particular relating to the length of time required to completely erect the crib. In this respect, U-shaped crib rods 8 and 9 (see FIGS. 6 and 7) are first required to be pivotably raised. Thereafter ropes 34 and 35 need then to be joined as shown in FIGS. 6 and 7. Subsequently, crib rods 8 and 9, which are telescoping rods, then need to be extended, requiring a spring biased button 37 to be depressed at each end of each of telescoping rods 8, 9 so as to extend the rods 8, 9 to thereby pull the ropes 34, 35 tight. Zippers 30 and 31 then need to be zipped shut to form the completely erected crib (Col. 3, lines 59-69, Col. 4, lines 1-15). This procedure, which is reversed on collapse of the unit, is time consuming, and accordingly reduces the speed at which the unit may be both erected or collapsed, thus decreasing the portability of the crib.